The present invention relates to new sulphur-containing polyethers based on (poly)thioalkylene oxides and polyalkylene oxides, their preparation from thiodiglycols and/or polythioglycols and polyalkylene oxides, and also their use as breakers for water-in-oil emulsions, in particular, as breakers for water-in-crude oil emulsions.
Petroleum is predominantly extracted in the form of aqueous emulsions, mainly in the form of water-in-oil emulsions, which are in general stabilized by substances contained in the petroleum and also by very finely divided solids extracted at the same time from the deposit. Frequently salts, e.g., sodium chloride, potassium chloride and/or magnesium chloride, are dissolved in the emulsified water. Transport costs, problems resulting from high viscosities of the emulsions and corrosion problems in the processing plants make it necessary essentially to dehydrate the crude oil before it is transported and/or before it is processed, i.e., to break the extracted emulsion.
The breaking of frequently very stable emulsions of this type takes place in general through the addition of interphase-active compounds, so-called demulsifiers or emulsion breakers, frequently assisted by heating the emulsion and/or additional application of electric fields.
In this case the residual water content, the salt and the ash content in the remaining crude oil and the residual oil content in the water separated off are critical for the quality of the emulsion breakers. The aim is to minimize these parameters while at the same time minimizing the concentration of the emulsion breaker used, its duration of action and its temperature of use.
The products used hitherto for the breaking of crude oil emulsions, e.g., block polymers of ethylene oxide and/or 1,2-propylene oxide (see, for example, U.S. Pat. No. 2,964,478), oxalkylated phenol resins (see, for example, U.S. Pat. No. 2,499,370 and U.S. Pat. No. 2,499,368) and block or mixed polymers of ethylene oxide and 1,2-propylene oxide crosslinked with diisocyanates, dicarboxylic acids, formaldehyde and/or diglycidyl ethers (see, for example, European Published Application 55,434 and European Published Application 55,433) are disadvantageous since they in general only partially fulfill the requirements. Thus, the breaking frequently proceeds slowly and incompletely unless the temperatures are relatively high. Known emulsion breakers are also frequently satisfactorily effective only for special emulsions, are not generally usable and are sufficiently effective only in relatively high dosages.